Such filter devices are available on the market in many prior art designs and embodiments. Among other things, they are used to filter out impurities in fluids, such as hydraulic fluid. Hydraulic fluid becomes contaminated with impurities during the installation and start-up of the respective hydraulic system. In addition to this initial contamination, contamination can also occur during operation, for example by impurities infiltrating the hydraulic tank due to inadequate tank ventilation, pipe openings, piston rod seals, and the like. In particular in hydraulic systems of work machines, such as earth movers, excavators, and the like, filtering returning fluids immediately in the area of the hydraulic tank, for example by installing the filter device directly in the tank as a return filter, can be useful. Document DE 10 2004 014 149 B4 discloses an example of a tank-installation filter.